Operators in patterns have incorrect priorities

[petrochenkov]

(Or at least unnatural priorities.)

Binary range operators have higher priority than unary operators like & or box.

#![feature(exclusive_range_pattern)]

fn main() {
    // Interpreted as (&0) .. (10), ERROR mismatched types
    let x = &0 .. 10;

    match &0 {
        &0 .. 10 => {} // OK?!
        _ => {}
    }
}

We can change the priorities for all the unstable kinds of ranges and come up with some deprecation story for stable BEGIN ... END.

[BubbaSheen]

I agree bianary operation is key at this point my friend.

…

On Feb 24, 2018 7:47 AM, "Vadim Petrochenkov" ***@***.***> wrote: (Or at least unnatural priorities.) Binary range operators have higher priority than unary operators like & or box. #![feature(exclusive_range_pattern)] fn main() { // Interpreted as (&0) .. (10), ERROR mismatched types let x = &0 .. 10; match &0 { &0 .. 10 => {} // OK?! _ => {} } } We can change the priorities for all the unstable kinds of ranges and come up with some deprecation story for stable BEGIN ... END. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#48501>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AhXLZqePgg1g85TIKYBMonnVrsrJZFf5ks5tYATegaJpZM4SR4T8> .

[durka]

This is weird. The behavior in expressions is the one I would expect. However, in patterns you aren't allowed to use parentheses for grouping (why not?) so there's no way to override the precedence.

[petrochenkov]

However, in patterns you aren't allowed to use parentheses for grouping (why not?) so there's no way to override the precedence.

That's why I submitted #48500 before fixing this :)

[durka]

Do you have any ideas for how to do that deprecation? If it's smooth enough we can stabilize ..= in patterns anyway and change them at the same time.

[petrochenkov]

@durka

Do you have any ideas for how to do that deprecation?

Compatibility warning, as usual?
I plan to prepare the fix this weekend, so it shouldn't delay stabilization of ..= in patterns too much.